18,436,052 research outputs found
Probing New Physics from Top-charm Associated Productions at Linear Colliders
The top-charm associated productions via , and collisions at linear colliders, which are extremely suppressed in the
Standard Model (SM), could be significantly enhanced in some extensions of the
SM. In this article we calculate the full contribution of the topcolor-assisted
technicolor (TC2) to these productions and then compare the results with the
existing predictions of the SM, the general two-Higgs-doublet model and the
Minimal Supersymmetric Model. We find that the TC2 model predicts much larger
production rates than other models and the largest-rate channel is , which exceeds 10 fb for a large part of the parameter
space. From the analysis of the observability of such productions at the future
linear colliders, we find that the predictions of the TC2 model can reach the
observable level for a large part of the parameter space while the predictions
of other models are hardly accessible.Comment: discussions added (version in Eur. Phys. J. C
Spin Polarizabilities of the Nucleon from Polarized Low Energy Compton Scattering
As guideline for forthcoming experiments, we present predictions from Chiral
Effective Field Theory for polarized cross sections in low energy Compton
scattering for photon energies below 170 MeV, both on the proton and on the
neutron. Special interest is put on the role of the nucleon spin
polarizabilities which can be examined especially well in polarized Compton
scattering. We present a model-independent way to extract their energy
dependence and static values from experiment, interpreting our findings also in
terms of the low energy effective degrees of freedom inside the nucleon: The
polarizabilities are dominated by chiral dynamics from the pion cloud, except
for resonant multipoles, where contributions of the Delta(1232) resonance turn
out to be crucial. We therefore include it as an explicit degree of freedom. We
also identify some experimental settings which are particularly sensitive to
the spin polarizabilities.Comment: 30 pages, 19 figure
Strange particle production in proton-proton collisions at TeV with ALICE at the LHC
The production of mesons containing strange quarks (K, ) and both
singly and doubly strange baryons (, Anti-, and
+Anti-) are measured at central rapidity in pp collisions at
= 0.9 TeV with the ALICE experiment at the LHC. The results are
obtained from the analysis of about 250 k minimum bias events recorded in 2009.
Measurements of yields (dN/dy) and transverse momentum spectra at central
rapidities for inelastic pp collisions are presented. For mesons, we report
yields () of 0.184 0.002 stat. 0.006 syst. for K and
0.021 0.004 stat. 0.003 syst. for . For baryons, we find
= 0.048 0.001 stat. 0.004 syst. for , 0.047
0.002 stat. 0.005 syst. for Anti- and 0.0101 0.0020 stat.
0.0009 syst. for +Anti-. The results are also compared with
predictions for identified particle spectra from QCD-inspired models and
provide a baseline for comparisons with both future pp measurements at higher
energies and heavy-ion collisions.Comment: 33 pages, 21 captioned figures, 10 tables, authors from page 28,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/387
Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at TeV
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb
collisions at = 2.76 TeV have been measured by the ALICE
Collaboration at the LHC. The data are presented for central and peripheral
collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross
section. The measured charged particle spectra in and GeV/ are compared to the expectation in pp collisions at the same
, scaled by the number of underlying nucleon-nucleon
collisions. The comparison is expressed in terms of the nuclear modification
factor . The result indicates only weak medium effects ( 0.7) in peripheral collisions. In central collisions,
reaches a minimum of about 0.14 at -7GeV/ and increases
significantly at larger . The measured suppression of high- particles is stronger than that observed at lower collision energies,
indicating that a very dense medium is formed in central Pb-Pb collisions at
the LHC.Comment: 15 pages, 5 captioned figures, 3 tables, authors from page 10,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/98
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
Signatures of Chiral Dynamics in Low Energy Compton Scattering off the Nucleon
We present a projector formalism which allows to define dynamical
polarizabilities of the nucleon from a multipole expansion of the nucleon
Compton amplitudes. We give predictions for the energy dependence of these
dynamical polarizabilities both from dispersion theory and from
leading-one-loop chiral effective field theory. Based on the good agreement
between the two theoretical frameworks, we conclude that the energy dependence
of the dynamical polarizabilities is dominated by chiral dynamics, except in
those multipole channels where the first nucleon resonance Delta(1232) can be
excited. Both the dispersion theory framework and a chiral effective field
theory with explicit Delta(1232) degrees of freedom lead to a very good
description of the available low energy proton Compton data. We discuss the
sensitivity of the proton Compton cross section to dynamical polarizabilities
of different multipole content and present a fit of the static electric and
magnetic dipole polarizabilities from low-energy Compton data up to omega=170
MeV, finding alpha_E=(11.04+-1.36)*10^(-4) fm^3, beta_M =(2.76-+1.36)*10^(-4)
fm^3.Comment: 43 pages, 13 figure
Observation of the TeV gamma-ray source MGRO J1908+06 with ARGO-YBJ
The extended gamma ray source MGRO J1908+06, discovered by the Milagro air
shower detector in 2007, has been observed for about 4 years by the ARGO-YBJ
experiment at TeV energies, with a statistical significance of 6.2 standard
deviations. The peak of the signal is found at a position consistent with the
pulsar PSR J1907+0602. Parametrizing the source shape with a two-dimensional
Gauss function we estimate an extension \sigma = 0.49 \pm 0.22 degrees,
consistent with a previous measurement by the Cherenkov Array H.E.S.S.. The
observed energy spectrum is dN/dE = 6.1 \pm 1.4 \times 10^-13 (E/4 TeV)^{-2.54
\pm 0.36} photons cm^-2 s^-1 TeV^-1, in the energy range 1-20 TeV. The measured
gamma ray flux is consistent with the results of the Milagro detector, but is
2-3 times larger than the flux previously derived by H.E.S.S. at energies of a
few TeV. The continuity of the Milagro and ARGO-YBJ observations and the stable
excess rate observed by ARGO-YBJ along 4 years of data taking support the
identification of MGRO J1908+06 as the steady powerful TeV pulsar wind nebula
of PSR J1907+0602, with an integrated luminosity above 1 TeV about 1.8 times
the Crab Nebula luminosity.Comment: 6 pages, accepted for pubblication by ApJ. Replaced to correct the
author lis
Identification of the TeV Gamma-ray Source ARGO J2031+4157 with the Cygnus Cocoon
The extended TeV gamma-ray source ARGO J2031+4157 (or MGRO J2031+41) is
positionally consistent with the Cygnus Cocoon discovered by -LAT at GeV
energies in the Cygnus superbubble. Reanalyzing the ARGO-YBJ data collected
from November 2007 to January 2013, the angular extension and energy spectrum
of ARGO J2031+4157 are evaluated. After subtracting the contribution of the
overlapping TeV sources, the ARGO-YBJ excess map is fitted with a
two-dimensional Gaussian function in a square region of , finding a source extension =
1.80.5. The observed differential energy spectrum is
photons cm
s TeV, in the energy range 0.2-10 TeV. The angular extension is
consistent with that of the Cygnus Cocoon as measured by -LAT, and the
spectrum also shows a good connection with the one measured in the 1-100 GeV
energy range. These features suggest to identify ARGO J2031+4157 as the
counterpart of the Cygnus Cocoon at TeV energies. The Cygnus Cocoon, located in
the star-forming region of Cygnus X, is interpreted as a cocoon of freshly
accelerated cosmic rays related to the Cygnus superbubble. The spectral
similarity with Supernova Remnants indicates that the particle acceleration
inside a superbubble is similar to that in a SNR. The spectral measurements
from 1 GeV to 10 TeV allows for the first time to determine the possible
spectrum slope of the underlying particle distribution. A hadronic model is
adopted to explain the spectral energy distribution.Comment: 16 pages, 3 figures, has been accepted by ApJ for publicatio
The Long-Term Economic Impact of Juvenile Criminal Activity
When the juvenile penal system is supposed to be focused on rehabilitation, how does committing crimes and being caught as juveniles affect their future economic success? In 2012, the FBI Arrest Statistics reports an estimated 1,319,700 minors were arrested. Since so many youths interact with the criminal system, it is vital for the strength of the workforce and for the quality of life of the minors to ensure that the system is rehabilitative. Using ordinary least squares regressions, I examine data collected from the National Longitudinal Survey of Youth\u27s 1997 cohort, and examine how interactions with the formal juvenile correctional system impacts a youth\u27s future income, taken in 2013. I find being caught for delinquent behavior, and subsequently being arrested, does significantly impact future income but only when education is not controlled for. Finally, I discuss the results and what they say about the juvenile criminal system, and suggest future policy
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